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How an objects can move?

  1. Apr 5, 2004 #1
    Perhaps, this a question will seem strange, but it is not such easy
    as what can seem at first sight. Moving of any object occurs in spacetime. Any object at a microscopic level represents set of particles placed in vacuum.
    Further.
    The particle having mass can’t selfpropagate. It can’t move without action of external force.
    Photons of light can selfpropagate in vacuum.
    There may be it is a unique way of moving in vacuum?
     
  2. jcsd
  3. Apr 5, 2004 #2

    ZapperZ

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    Not even...

    What if an object defragments into 2 or more objects? What if the sum of all the rest masses of the fragments are less than the mass of the original object, meaning there are leftover energy converted into kinetic energy (this happens in fission processes)? The fragments are now moving through space with respect to the rest frame of the original object without any "action of external force".

    If you think about it, it is more unusual for something to NOT be moving or spinning, rather than the other way around.

    Zz.
     
  4. Apr 6, 2004 #3
    Then these fragments having received an initial pulse will move.
    The pulse is action of external force concerning a set of atoms of each fragment.
    But it isn’t the matter.
    The matter is:
    how any object except of light can move in vacuum?
     
  5. Apr 6, 2004 #4

    ZapperZ

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    The initial condition of the universe.

    Zz.
     
  6. Apr 6, 2004 #5

    Doc Al

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    What is the basis of this statement, which contradicts Newton's 1st law?
     
  7. Apr 6, 2004 #6

    russ_watters

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    I think we've had this discussion before: the idea is that when you get down to the QM of it, contact forces are electromagnetic. Not a big issue though.
     
  8. Apr 6, 2004 #7

    ZapperZ

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    However, I don't think this is what is being asked. Vacuum fluctuations that might cause Casimir-type effects are highly improbable, and does not, for example, explain why things as big as a tennis ball or a planet moves. So the original question on why "object" moves can't be explaned by this.

    My original response to this is still valid, i.e. what's the big deal with things that are moving. What is more unusual is to find objects in space that aren't moving. There is a very small phase space where something else in the universe shares the same inertial reference frame as we do. Even when you have something that isn't moving, translating that to another coordinate system that is moving will then make the object moves, but other than that, the physics and the physical laws hasn't changed or remain covariant. So what's the big deal that the object is "moving" or not moving?

    Zz.
     
  9. Apr 7, 2004 #8
    My understanding is that photons are the result of accelerating the source of an electric field (like all electromagnetic phenomena). If you don't put energy in ("external force") you won't get energy out (photons, in this case). The movement of the photons is as dependent upon "action of external force" as any motion is.
     
  10. Apr 7, 2004 #9

    ZapperZ

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    Not necessarily. While it is true that you can create EM radiation via an accelerating charge, you can also have such radiation via atomic transition. Your fluorescent light bulb works this way, and so do most of those multicolored neon signs. In this case, there are no "accelerating charge" [as long as someone doesn't get me started on "orbiting" electrons in an atom].

    Zz.
     
  11. Apr 7, 2004 #10
    Yes, this is true, however this still requires an imput: in order to drop to a lower orbital and release a photon the electrons have, first, to be "pumped" to a higher orbital. Again there is a requirement for an "external force" to get it started.
     
  12. Apr 7, 2004 #11

    turin

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    I think I'm agreeing with ZapperZ: motion of a massive object is arbitrary. If the object is at rest in one coordinate system, it is simply a matter of a Lorentz transformation for the object to be in motion. A Lorentz transformation does not require any physics; the coordinatization is a mathematical abstraction, and therefore so is motion. What's the big deal?
     
  13. Apr 7, 2004 #12

    ZapperZ

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    Yes, but this is a matter of conservation of energy, something I don't think I was disputing in my previous posting. However, the creation of photons do not always require an "accelerating charge" per Maxwell equations. There are no "accelerating charge" in an atomic transition. Furthermore, the system of particle-antiparticle, for example, requires no "external input/force" to anhilate and generate photons.

    Zz.
     
  14. Apr 7, 2004 #13
    You are correct: I did not cover every possible way a photon could be generated in my first post. That is why I said "Yes, this is true," after I quoted your statement about atomic transitions.

    I am concerned that by the use of the term "self propagating" Dmitriyev is implying that the photon has energy that doesn't first come from somewhere else. His original question seemed to me to arise from pondering the difference in the motion of the photon and the motion of mass. He speaks of mass as requiring an outside force to set it in motion, which is true in the Newtonian sense of changing its inertia, but he seems to feel that the photon is not equally dependent on an imput of force or energy to get it started.


    I am not familiar with this particle-antiparticle means of producing a photon, but as long as you aren't disputing conservation of energy with it then the resultant photons represents energy transduced from something else.
     
  15. May 6, 2004 #14
    As I can see, nobody knows how an objects can move. My regrets.
     
  16. May 8, 2004 #15

    Gokul43201

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    First God made things and then God said "let things move". Since then, all things have been moving.
     
  17. May 11, 2004 #16
    So, only God knows?
     
  18. May 12, 2004 #17
    As it seems to me :
    To have an opportunity to move in any direction, any particle should have components of fluctuations conterminous with a force vector. If the such component is absent then the particle cannot move in this direction.
    Since the vector of force may have an any direction, than fluctuations in a particle should have components of all directions too. To this condition in the maximal degree corresponds the spherical (pseudo spherical) form of atom as the sum of all component.

    Michael.
     
    Last edited: May 15, 2004
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